males will invest resources in any child that might be theirs

The words "invest resources" mean something different for animals and humans. For animal male it simply means: allow the child walk on your territory; protect the child from predator attack; give the child some food. I would expect similar instincts from a human male.

The difference is, we expect much more from human males, which has no base in instincts. We expect human male to find a better-paying job (with longer working hours or less pleasant work), and use the money to support child's various needs, such as e.g. education.

If you have a piece of bread in your hand, and there is a hungry 3 years old child (possibly biologically yours) near you, the instinct tells you to give the bread to the child. But the same instinct does not tell you to change your job so you can pay your 18 years old child better college. We give our children far more than what our instincts say, and we also care about them much longer.